Renewable fuels are fuels produced from renewable resources. Such fuels include biodiesel. One potential feedstock source for preparing biodiesel is to use a feedstock that contains glycerides, which are present in many renewable feed sources, including many vegetable oils and animal fats. This feedstock typically contains triglycerides as well as amounts of di- and monoglycerides. Typical triglycerides have a glycerol backbone with up to three long-chain fatty acids covalently bound to the glycerol backbone through an ester linkage. The glycerol backbone may be separated from the fatty acids, and the fatty acids may have a carbon chain length that is suitable for use, typically after further processing, as for example fuels, additives, and lubricants. Often the glyceride feedstock undergoes catalytic deoxygenation under hydrogen pressure, which provides hydrocarbons with a chain length suitable for use as fuels or lubricants, as well as propane and/or propylene from the glycerol backbone.
WO 2013/148906 (to ExxonMobil Research and Engineering Company) relates to the processing of feeds containing triglycerides from renewable sources to produce an olefinic diesel fuel product and propylene. It is described in [0086]-[0089] that propylene can be separated from gas phase components, which may include H2O, CO2, CO, H2, H2S, N2, light ends and propane. It involves separation of the gas phase products from the liquid products from the deoxygenation reaction. Propylene is then separated from the remaining gas phase components. Cryogenic distillation columns are indicated as being beneficial for separation of propane from propylene, and it is suggested that another option for separating propylene from the gas phase mixture could be to use a gas separation train similar to the separation used in some fluid catalytic cracking reaction systems.
U.S. Pat. No. 8,318,996 B2 (to UOP LLC) relates to methods for treating a hydrogen recycle gas in a process for converting biorenewable feedstock into green diesel comprising removing light hydrocarbons from the hydrogen recycle gas by contacting the hydrogen recycle gas with a sponge oil. Propane is then recovered from a propane-rich sponge oil by a propane fractionation unit.
Thus, there remains a need for further methods that can separate at least propane from hydrogen.